Method of the production of neutral esters of phosphoric acid



Patented Nov. 11, 1947 METHOD 01* T PRODUCTION F NEU- TEAL ESTERS 0FPHOSPHQRKC AEKD I David 0. Hull and Albert H. dgett; Kingsport, Tenn,assignors to Eastman Kodak Company, Rochester, N.,Y., a corporation ofNew Jersey Application December 8, 1943,

Serial No. 513,471

, phenols and either phosphorous pentachlori'de or P205. These variousmethods whichhave been suggested heretofore have involved either the useof expensive starting materials or dificulty and I expense in refiningthe products obtained. Also,

in many cases side reactions have occurred cutting down the yields.

One object of our invention is to provide a method of preparingphosphoric acid esters in an economical manner. This economy is realizedby the use of less expensive starting material, by obtaining the productin good yield, and by recovering the product merely by vacuumdistillation in a form suiiiciently pure for use commercially.

We have found that the reaction of an alkyl meta phosphate orpyrophosphate with an acetal at an elevated temperature results inneutral esters of phosphoric acid which are of value for the varioususes to which such compounds are put at the present time. The reactionmay either be carried out without a catalyst or may be promoted by theuse of an esteriflcation catalyst if desired.

The alkyl or aryl meta phosphate or pyrophosphate or their mixtureemployed as the starting materials for our process may be prepared, forinstance, by reacting P205 withan ether, the latter not being present inmore than a theoretical amount or by treating triethyl phosphate withP205 to convert it to the meta phosphate or pyrophosphate. The alkylmeta phosphate or the pyrophosphate or their mixture and the acetal aremixed together and subjected to a temperature of at least 65 C. forseveral hours so as to form the desired product. Instead of ethyl metaphosphate 'or pyrophosphate, other alkyl meta phosphates orpyrophosphates may be employed such as those in which the alkyl group ismethyl, normal or isopropyl or normal or isobutyl. If desired, an arylmeta phosphate or pyrophosphate may be employed such as phenyl or cresylmeta phosphate or pyrophosphate.

The acetal employed may be any of the com- (cl. etc-4st) pounds of thistype, a simple and effective compound which may be employed being ethylbutyral. However, other acetals such as ethyl propional, methyl butyral,or in fact any of the 5 acetals particularly those prepared from anaidehyde having 4 ormore carbon atoms may be employed.

As the acetals are not decidedly low boiling ordinarily the reaction inaccordance with our pressure and it is preferred to carry out thereaction under moderate temperature conditions. Nevertheless it is to beunderstood that higher temperatures are not precluded, the onlycriterion being that the temperature be limited so as to not generatepressure which would be destructive of equipment or materials. We havefound that the reaction of the acetal and a metaphosphate orpyrophosphate takes place readily and, therefore, a, wide temperaturelatitude is permissible. In practical operation a temperature of 80 C.is ordinarily preferred. However, ranging from 0 0. up to 200 C. areuseful in the carrying out of our process, the most suitabletemperatures in this range being a matter of selection depending on thereaction materials employed, particularly the acetals chosen.

The alkyl meta phosphate or pyrophosphate employed as a startingmaterial is preferably prepared immediately prior to use and thereaction mass containing that material is employed in the reaction. Forinstance, ethyl meta'phosphate and pyrophosphate may be prepared byreacting P205 more than theoretical amount. However, if desired,triethyl phosphate may be prepared in accordance with the methoddescribed in Hull and Snodgrass application, Serial No. 513,472, nowUnited States Patent 2,407,279, dated Sept. 10, 1946, filed of even dateand the ethyl meta phosphate may be prepared therefrom by reacting thetriethyl phosphate with P205. If desired, the triethyl phosphate usedmay be prepared by reactions known in the prior art. The time employedfor the reaction is not critical depending upon the vigorousness of thetreatment and whether or not a catalyst is employed. Any commonly knownesteriflcation catalyst may be patible with the constituents of thereaction mass.

Some of the catalysts which may be mentioned as suitable are sulfuricacid, phosphoric acid, zinc;

invention may be carried out at atmospheric temperatures and diethylether, the latter being present in no used to promote'the reactionproviding it is comtral ester of phosphoric acid in accordance with ourinvention.

Example acid esters are obtained in a more pure state than by methodspreviously described in the prior art. Also, the phosphoric acid estersprepared in accordance with our procedure maybe separated from thereaction ingredients by vacuum distillation thus avoiding the necessityof expensive purifying procedures.

We claim: 1. The method of preparing triethyl phosphate which comprisestreating ethyl metaphosphate with ethyl butyral.

2. The method of preparing triethyl phosphate which comprises treatingtetraethylpyrophosphate with ethyl butyral.

3. The method of preparing a neutral ester of orthophosphoric acid whichcomprises treating an ester of the group consisting of alkylmetaphosphates and alkyl pyrophosphates, the alkyl being of 1-4 carbonatoms, with an acetal of 6-8 carbon atoms at 0-200 C.

4. The method of preparing a neutral ester of orthophosphoric acid whichcomprises treating an alkyl metaphosphate, the alkyl being of 1 to 4carbon atoms with an acetal of 6-8 carbon atoms at 0-200 C.

5. The method of preparing a neutral ester of orthophosphoric acid whichcomprises treating an alkyl pyrophosphate, the alkyl being of l-4 carbonatoms with an acetal of 6-8 carbon atoms at 0-200 0.

6. The method of preparing a neutral ester of orthophosphoric acid whichcomprises treating an ester of the group consisting of ethyl metacarbonatoms at 0-200 C.

'4 phosphates and ethyl pyrophosphates with an acetal of 6-8 carbonatoms at 0-200 C.

7. The method of preparing a neutral ester oi? orthophosphoric acidwhich comprises treating an ester of the group consisting of alkylmetaphosphates and alkyl pyrophosphates, the aikyl being of 1-4 carbonatoms with ethyl butyral at 0-200 C.

8. The method of preparing a neutral ester of orthophosphoric acid whichcomprises treating an ester of the group consisting of alkyl meta-vphosphate and alkyl pyrophosphate, the alkyl being of 1-4 carbon atomswith ethyl propional.

9. The method of preparing a, neutral ester of orthophosphoric acidwhich comprises treating an ester of the group consisting of alkylmetaphosphate and alkyl pyrophosphate, the alkyl being of 1-4 carbonatoms with methyl butyral.

10. A method of preparing a neutral ester of orthophosphoric acid whichcomprises treating ethyl metaphosphate with an acetal of 6-8 carbonatoms at 0-200" 0.

11; A method of preparing a neutral ester of orthophosphoric acid whichcomprises treating tetra ethyl pyrophosphate with an acetal of 6-8 DAVIDC. HUIL. ALBERT H. AGE 'IT.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS OTHER REFERENCES Chemical Abstracts, vol. 31,1937, pp. 2166-2167 (abstract of article byWagner-Jauregg et al. inBerichte).

Feiser et al., Organic Chemistry, page 32 (1944), Heath 8: Co.,publishers, Boston.

Science News Letter, March 22, 1947, page 188.

